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United States Patent |
6,015,012
|
Reddick
|
January 18, 2000
|
In-situ polymerization method and apparatus to seal a junction between a
lateral and a main wellbore
Abstract
An improved method and apparatus for sealing a junction between a central
and lateral wellbore is provided. In a broad aspect, the method of the
present invention includes installing a polymerizable sealing sleeve
within a first casing in a central wellbore at a junction between the
first casing and a second casing in a lateral wellbore. After the sealing
sleeve has been installed and allowed to cure, a milling tool is used to
mill a window through a sidewall of the sealing sleeve and flush with the
inner diameter of the second casing. The sealing sleeve may be used alone
to establish a primary seal, or in combination with cement or other
sealing substance, as used heretofore in prior art sealing methods, as a
back-up seal. The sealing sleeve of the present invention may be provided
with at least one orienting means to enable the second casing to be
located and to direct a well tool thereinto.
Inventors:
|
Reddick; Mark S. (Houston, TX)
|
Assignee:
|
Camco International Inc. (Houston, TX)
|
Appl. No.:
|
920994 |
Filed:
|
August 29, 1997 |
Current U.S. Class: |
166/313; 166/50; 166/117.5 |
Intern'l Class: |
E21B 007/06 |
Field of Search: |
166/297,298,50,387,378,313,117.5
|
References Cited
U.S. Patent Documents
5353876 | Oct., 1994 | Curington et al. | 166/313.
|
5427177 | Jun., 1995 | Jordan, Jr. et al.
| |
5462120 | Oct., 1995 | Gondouin.
| |
5474131 | Dec., 1995 | Jordan, Jr. et al.
| |
5477925 | Dec., 1995 | Trahan et al.
| |
5531270 | Jul., 1996 | Fletcher et al.
| |
5564503 | Oct., 1996 | Longbottom et al.
| |
5566763 | Oct., 1996 | Williamson et al.
| |
5613559 | Mar., 1997 | Williamson et al.
| |
5615740 | Apr., 1997 | Comeau et al.
| |
5787987 | Aug., 1998 | Forsyth et al. | 166/313.
|
Foreign Patent Documents |
WO 94/03699 | Feb., 1994 | WO.
| |
Primary Examiner: Neuder; William
Assistant Examiner: Walker; Zakiya
Attorney, Agent or Firm: Tobor, Goldstein & Healey, L.L.P.
Parent Case Text
RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application Ser.
No. 60/024,960, filed Aug. 30, 1996.
Claims
I claim:
1. A method of sealing a junction between a central wellbore having a first
casing and at least one lateral branch wellbore comprising the steps of:
running and setting a lower whipstock in the first casing;
running and setting a window mill pilot in the first casing;
milling a window in the first casing;
drilling a lateral branch wellbore through the casing window out from the
central wellbore;
removing the window mill pilot from the first casing;
running and setting an upper whipstock in the first casing adjacent and
above the lower whipstock;
running a second casing into the first casing, through the casing window,
and into the lateral branch wellbore such that a stub portion of the
second casing extends from the lateral branch wellbore through the casing
window and into the first casing;
milling the stub portion of the second casing flush with an inner diameter
of the first casing;
retrieving the upper whipstock from the first casing;
running and installing an in-situ polymerizable sleeve in the first casing
adjacent the junction of the first and second casings;
running and setting a window remill pilot inside the in-situ polymerizable
sleeve adjacent the junction of the first and second casings;
milling a window in the in-situ polymerizable sleeve;
retrieving the window remill pilot from inside the in-situ polymerizable
sleeve; and
removing the lower whipstock from the first casing.
2. The method of claim 1, wherein an upper surface of the upper whipstock
is aligned with a lower edge of the casing window when the upper whipstock
is set in place.
3. The method of claim 1, furthering including the step of cleaning the
first casing after the step of milling the stub portion flush with the
inner diameter of the first casing.
4. The method of claim 1, wherein the window in the in-situ polymerizable
sleeve is milled flush with an inner diameter of the second casing.
5. The method of claim 1, wherein the lower whipstock is removed by
retrieving it through the in-situ polymerizable sleeve.
6. The method of claim 1, wherein the lower whipstock is removed by
drilling it out.
7. The method of claim 1, further including the step of using a sealing
substance to set the second casing in place within the lateral branch
wellbore after it has been positioned and before its stub portion is
milled flush with the inner diameter of the first casing, whereby the
polymerizable sleeve operates as a back-up seal to the sealing substance.
8. The method of claim 7, wherein the sealing substance is cement.
9. The method of claim 1, wherein the sleeve further includes at least one
orienting device for locating the second casing when access is desired
thereto, and for selectively directing a well tool into the second casing.
10. The method of claim 1, wherein the sleeve further includes a first and
a second orienting device, the first orienting device being attached to a
first end of the sleeve, and the second orienting device being attached to
a second end of the sleeve, the orienting devices being used to locate the
second casing when access is desired thereto, and to selectively direct a
well tool into the second casing.
11. The method of claim 1, wherein the sleeve further includes:
a cylindrical body having a longitudinal bore therethrough constructed of
fibers and polymerizable resins;
a drillable sidewall in the cylindrical body; and
a resilient outer skin substantially covering the cylindrical body.
12. A method of sealing a junction between a central wellbore having a
first casing and at least one lateral branch wellbore comprising the steps
of:
running and setting a whipstock in the first casing;
diverting a milling tool off the whipstock to mill a window in the first
casing;
drilling a lateral branch wellbore through the casing window out from the
central wellbore;
running a second casing into the first casing, and diverting the second
casing off the whipstock through the casing window and into the lateral
branch wellbore such that a stub portion of the second casing extends from
the lateral branch wellbore through the casing window and into the first
casing;
milling the stub portion of the second casing flush with an inner diameter
of the first casing;
running and installing an in-situ polymerizable sleeve in the first casing
adjacent the junction of the first and second casings;
milling a window in the in-situ polymerizable sleeve adjacent the casing
window; and,
removing the whipstock from the first casing.
13. The method of claim 12, furthering including the step of cleaning the
first casing after the step of milling the stub portion flush with the
inner diameter of the first casing.
14. The method of claim 12, wherein the window in the in-situ polymerizable
sleeve is milled flush with an inner diameter of the second casing.
15. The method of claim 12, wherein the whipstock is removed by retrieving
it through the in-situ polymerizable sleeve.
16. The method of claim 12, wherein the whipstock is removed by drilling it
out.
17. The method of claim 12, further including the step of using a sealing
substance to set the second casing in place within the lateral branch
wellbore after it has been positioned and before its stub portion is
milled flush with the inner diameter of the first casing, whereby the
polymerizable sleeve operates as a back-up seal to the sealing substance.
18. The method of claim 17, wherein the sealing substance is cement.
19. The method of claim 12, wherein the sleeve further includes at least
one orienting device for locating the second casing when access is desired
thereto, and for selectively directing a well tool into the second casing.
20. The method of claim 12, wherein the sleeve further includes a first and
a second orienting device, the first orienting device being attached to a
first end of the sleeve, the second orienting device being attached to a
second end of the sleeve, and the orienting devices being used to locate
the second casing when access is desired thereto and to selectively direct
a well tool into the second casing.
21. The method of claim 12, wherein the sleeve further includes:
a cylindrical body having a longitudinal bore therethrough constructed of
fibers and polymerizable resins;
a drillable sidewall in the cylindrical body; and
a resilient outer skin substantially covering the cylindrical body.
22. In a central wellbore having at least one lateral branch wellbore
extending therefrom, the central wellbore having a first casing disposed
therein, the first casing having a casing window disposed therein, the
lateral branch wellbore having a second casing disposed therein and
adjacent the casing window to form a junction between the first and second
casings, an improved method of sealing the junction, wherein the
improvement comprises the steps of:
installing an in-situ polymerizable sleeve in the first casing adjacent the
junction so as to cover the casing window and seal the junction, the
sleeve including at least one orienting device for locating the second
casing when access is desired thereto, and for selectively directing a
well tool into the second casing; and,
milling a window in the in-situ polymerizable sleeve.
23. The method of claim 22, further including the steps of:
running and setting a window remill pilot inside the in-situ polymerizable
sleeve adjacent the junction after the sleeve is installed and before the
sleeve window is milled; and
retrieving the window remill pilot from inside the in-situ polymerizable
sleeve after the sleeve window is milled.
24. The method of claim 22, wherein the window in the in-situ polymerizable
sleeve is milled flush with an inner diameter of the second casing.
25. The method of claim 22, wherein the sleeve further includes a first and
a second orienting device, the first orienting device being attached to a
first end of the sleeve, and the second orienting device being attached to
a second end of the sleeve, the orienting devices being used to locate the
second casing when access is desired thereto, and to selectively direct a
well tool into the second casing.
26. The method of claim 22, wherein the junction has been previously sealed
by a sealing substance and the in-situ polymerizable sleeve functions as a
backup seal to the previous seal.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to subsurface well completion equipment and,
more particularly, to a method and apparatus for sealing the junction
between a main wellbore and at least one lateral wellbore drilled from the
main wellbore.
2. Description of the Related Art
In recent years, those engaged in the exploration of oil and gas have
determined that production from a central wellbore can be economically
enhanced by drilling one or more lateral branch wellbores out from the
central wellbore. To drill a lateral wellbore, an opening or window must
first be cut through a casing in the central wellbore at a location where
it is desired to start drilling the lateral wellbore. This can be done
before or after the casing is lowered into the main wellbore. A mechanical
diverter, commonly referred to as a whipstock, is then placed inside the
main wellbore just below the casing window. If the casing window is to be
cut after the casing is already cemented in place in the central wellbore,
then a milling tool is guided by the whipstock to mill the casing window
in the casing. A drilling tool is then lowered into the main wellbore and
diverted into and through the casing window by the whipstock. The drilling
tool then continues on to drill the lateral wellbore. When the lateral
wellbore has been drilled, the drilling tool is removed, and a casing
string is lowered into the main wellbore, through the casing window, and
into the lateral wellbore. It is very important that a seal be established
at the junction of the main wellbore casing and the lateral wellbore
casing; the present invention is directed to this need.
One approach used heretofore to seal the junction has been to simply pump
cement down the main wellbore casing, into the lateral wellbore casing,
down to the end of the lateral wellbore casing, back up into the annulus
between the lateral wellbore and the lateral wellbore casing, and to the
annulus adjacent the junction between the main wellbore casing and the
lateral wellbore casing. Others have attempted to seal the junction in a
similar manner, but with substances other than cement. The apparatus and
method of the present invention, as more fully described below, were
developed to provide an improved approach to sealing the junction between
a main and lateral wellbores. A further object of the apparatus and method
of the present invention is to include a means of locating the junction
between the main and lateral wellbores to enable reentry into the lateral
wellbore.
SUMMARY OF THE INVENTION
In accordance with the present invention, the foregoing objectives have
been achieved by the present method and apparatus. In a broad aspect, the
present invention may be a method of sealing a junction between a central
wellbore having a first casing and at least one lateral branch wellbore
comprising the steps of: running and setting a lower whipstock in the
first casing; running and setting a window mill pilot in the first casing;
milling a window in the first casing; drilling a lateral branch wellbore
through the casing window out from the central wellbore; removing the
window mill pilot from the first casing; running and setting an upper
whipstock in the first casing adjacent and above the lower whipstock;
running a second casing into the first casing, through the casing window,
and into the lateral branch wellbore such that a stub portion of the
second casing extends from the lateral branch wellbore through the casing
window and into the first casing; milling the stub portion of the second
casing flush with an inner diameter of the first casing; retrieving the
upper whipstock from the first casing; running and installing an in-situ
polymerizable sleeve in the first casing adjacent the junction of the
first and second casings; running and setting a window remill pilot inside
the in-situ polymerizable sleeve adjacent the junction of the first and
second casings; milling a window in the in-situ polymerizable sleeve;
retrieving the window remill pilot from inside the in-situ polymerizable
sleeve; and removing the lower whipstock from the first casing. Another
feature of this aspect of the present invention is that an upper surface
of the upper whipstock may be aligned with a lower edge of the casing
window when the upper whipstock is set in place. Another feature of this
aspect of the present invention is that the method may further include the
step of cleaning the first casing after the step of milling the stub
portion flush with the inner diameter of the first casing. Another feature
of this aspect of the present invention is that the window in the in-situ
polymerizable sleeve may be milled flush with an inner diameter of the
second casing. Another feature of this aspect of the present invention is
that the lower whipstock may be removed by retrieving it through the
in-situ polymerizable sleeve. Another feature of this aspect of the
present invention is that the lower whipstock may be removed by drilling
it out. Another feature of this aspect of the present invention is that
the method may further include the step of using a sealing substance to
set the second casing in place within the lateral branch wellbore after it
has been positioned and before its stub portion is milled flush with the
inner diameter of the first casing, whereby the polymerizable sleeve
operates as a back-up seal to the sealing substance. Another feature of
this aspect of the present invention is that the sealing substance may be
cement. Another feature of this aspect of the present invention is that
the sleeve may further include at least one orienting device for locating
the second casing when access is desired thereto, and for selectively
directing a well tool into the second casing. Another feature of this
aspect of the present invention is that the sleeve may further include a
first and a second orienting device, the first orienting device being
attached to a first end of the sleeve, and the second orienting device
being attached to a second end of the sleeve, the orienting devices being
used to locate the second casing when access is desired thereto, and to
selectively direct a well tool into the second casing. Another feature of
this aspect of the present invention is that the sleeve may further
include: a cylindrical body having a longitudinal bore therethrough
constructed of fibers and polymerizable resins; a drillable sidewall in
the cylindrical body; and a resilient outer skin substantially covering
the cylindrical body.
In another aspect, the present invention may be a method of sealing a
junction between a central wellbore having a first casing and at least one
lateral branch wellbore comprising the steps of: running and setting a
whipstock in the first casing; diverting a milling tool off the whipstock
to mill a window in the first casing; drilling a lateral branch wellbore
through the casing window out from the central wellbore; running a second
casing into the first casing, and diverting the second casing off the
whipstock through the casing window and into the lateral branch wellbore
such that a stub portion of the second casing extends from the lateral
branch wellbore through the casing window and into the first casing;
milling the stub portion of the second casing flush with an inner diameter
of the first casing; running and installing an in-situ polymerizable
sleeve in the first casing adjacent the junction of the first and second
casings; milling a window in the in-situ polymerizable sleeve adjacent the
casing window; and, removing the whipstock from the first casing. Another
feature of this aspect of the present invention is that the method may
further include the step of cleaning the first casing after the step of
milling the stub portion flush with the inner diameter of the first
casing. Another feature of this aspect of the present invention is that
the in-situ polymerizable sleeve is milled flush with an inner diameter of
the second casing. Another feature of this aspect of the present invention
is that the whipstock may be removed by retrieving it through the in-situ
polymerizable sleeve. Another feature of this aspect of the present
invention is that the whipstock may be removed by drilling it out. Another
feature of this aspect of the present invention is that the method may
further include the step of using a sealing substance to set the second
casing in place within the lateral branch wellbore after it has been
positioned and before its stub portion is milled flush with the inner
diameter of the first casing, whereby the polymerizable sleeve operates as
a back-up seal to the sealing substance. Another feature of this aspect of
the present invention is that the sealing substance may be cement. Another
feature of this aspect of the present invention is that the sleeve may
further include at least one orienting device for locating the second
casing when access is desired thereto, and for selectively directing a
well tool into the second casing. Another feature of this aspect of the
present invention is that the sleeve may further include a first and a
second orienting device, the first orienting device being attached to a
first end of the sleeve, the second orienting device being attached to a
second end of the sleeve, and the orienting devices being used to locate
the second casing when access is desired thereto and to selectively direct
a well tool into the second casing. Another feature of this aspect of the
present invention is that the sleeve may further include: a cylindrical
body having a longitudinal bore therethrough constructed of fibers and
polymerizable resins; a drillable sidewall in the cylindrical body; and a
resilient outer skin substantially covering the cylindrical body.
In another aspect, the present invention may be, in a central wellbore
having at least one lateral branch wellbore extending therefrom, the
central wellbore having a first casing disposed therein, the first casing
having a casing window disposed therein, the lateral branch wellbore
having a second casing disposed therein and adjacent the casing window to
form a junction between the first and second casings, an improved method
of sealing the junction, wherein the improvement comprises the steps of:
installing an in-situ polymerizable sleeve in the first casing adjacent
the junction so as to cover the casing window and seal the junction; and,
milling a window in the in-situ polymerizable sleeve. Another feature of
this aspect of the present invention is that the method may further
include the steps of: running and setting a window remill pilot inside the
in-situ polymerizable sleeve adjacent the junction after the sleeve is
installed and before the sleeve window is milled; and retrieving the
window remill pilot from inside the in-situ polymerizable sleeve after the
sleeve window is milled. Another feature of this aspect of the present
invention is that the window in the in-situ polymerizable sleeve may be
milled flush with an inner diameter of the second casing. Another feature
of this aspect of the present invention is that the sleeve may further
include at least one orienting device for locating the second casing when
access is desired thereto, and for selectively directing a well tool into
the second casing. Another feature of this aspect of the present invention
is that the sleeve may further include a first and a second orienting
device, the first orienting device being attached to a first end of the
sleeve, and the second orienting device being attached to a second end of
the sleeve, the orienting devices being used to locate the second casing
when access is desired thereto, and to selectively direct a well tool into
the second casing. Another feature of this aspect of the present invention
is that the junction has been previously sealed by a sealing substance and
the in-situ polymerizable sleeve functions as a backup seal to the
previous seal.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevation view of a cased central wellbore.
FIG. 2 is an elevation view showing a lower whipstock and a window mill
pilot positioned within the casing, and a window that has been milled into
a section of the casing.
FIG. 3 is an elevation view showing a lateral wellbore that has been
drilled adjacent the casing window shown in FIG. 2.
FIG. 4 is an elevation view showing an upper whipstock that has been
positioned adjacent the casing window shown in FIGS. 2 and 3--after the
window mill pilot shown in FIGS. 2 and 3 has been removed--to guide a
section of casing string (not shown in this Figure) into the lateral
wellbore shown in FIG. 3.
FIG. 5 is an elevation view showing a section of casing string lowered into
the lateral wellbore with a stub portion thereof extending into the
central wellbore.
FIG. 6 is an elevation view showing the lateral wellbore casing in place
after the stub portion shown in FIG. 5 has been milled off flush with the
inner diameter of the central wellbore casing.
FIG. 7 is an elevation view showing an in-situ polymerizable sealing sleeve
positioned adjacent the junction of the central and lateral wellbores.
FIG. 8 is an elevation view showing a remilling tool located inside the
in-situ polymerizable sleeve and adjacent the casing window.
FIG. 9 is an elevation view showing a window that has been cut into the
in-situ polymerizable sleeve adjacent the casing window, with the
remilling tool shown in FIG. 8 still in place inside the in-situ
polymerizable sleeve.
FIG. 10 is an elevation view similar to FIG. 9 except that the remilling
tool and lower whipstock have been removed in this Figure.
While the invention will be described in connection with the preferred
embodiments, it will be understood that it is not intended to limit the
invention to those embodiments. On the contrary, it is intended to cover
all alternatives, modifications, and equivalents as may be included within
the spirit and scope of the invention as defined by the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
Referring to the drawings in detail, wherein like numerals denote identical
elements throughout the several views, the method and apparatus of the
present invention will now be explained, beginning with FIG. 1, which
depicts a central wellbore 20 with a first casing 22 cemented in place
therein. In a broad aspect, the first step of the method of the present
invention is to create an opening in the first casing 22, if the first
casing 22 is not already provided with such an opening. The opening should
be located where it is desired to start drilling a lateral wellbore. In a
specific embodiment of the method of the present invention, as shown in
FIG. 2, an opening may be created by first running and setting a lower
whipstock 24 having an upper inclined surface 25 in the first casing 22
below the location where it is desired to start drilling a lateral
wellbore generally adjacent to a hydrocarbon producing formation (not
shown). The whipstock 24 should be oriented (by the use, for example, of
CCL technology, as known in the art) at the x,y,z coordinates needed to
direct the lateral wellbore to the target production zone (not shown). The
structure and operation of whipstocks, such as the lower whipstock 24, and
the manner in which whipstocks are run, oriented, and set within a
wellbore casing, are well known to those of ordinary skill in the art.
After the lower whipstock 24 has been set, the next step, as shown in FIG.
2, is to run and set a window mill pilot 26 having a lower inclined
surface 27 in the central wellbore 20. The window mill pilot 26 is located
above and adjacent the lower whipstock 24. The lower inclined surface 27
of the window mill pilot 26 mates with the upper inclined surface 25 of
the lower whipstock 24, so as to position the window mill pilot 26 in its
proper x,y,z orientation. The window mill pilot 26 is provided with an
upper contoured surface 28, and an inner profile 30 for mating with a
retrieving tool (not shown). The structure and operation of window mill
pilots, such as the window mill pilot 26, and the manner in which they are
run, oriented, and set within a wellbore casing, are well known to those
of ordinary skill in the art. After the window mill pilot 26 has been set,
the next step, as shown in FIG. 2, is to use a milling tool (not shown) to
mill a window 32 in the first casing 22. The structure and operation of
milling tools, and the manner in which they are used to mill windows in
casing, are well known to those of ordinary skill in the art.
Alternatively, the step of running and setting the window mill pilot 26
may be omitted, and the milling tool (not shown) may be diverted by the
lower whipstock 24 to mill the window 32 in the first casing 22.
After the window 32 has been milled in the first casing 22, the next step,
as shown in FIG. 3, is to drill a lateral branch wellbore 34. To
accomplish this task, a drilling tool (not shown) is lowered into the
first casing 22 and is guided along the contoured surface 28 of the window
mill pilot 26--or by the lower whipstock 24 if the window mill pilot 26 is
not used--through the casing window 32. The drilling tool (not shown) then
continues on to drill the lateral wellbore 34. When the lateral wellbore
34 has been drilled, the drilling tool (not shown) is removed, as is the
window mill pilot 26. Next, as shown in FIG. 4, an upper whipstock 36
having a lower inclined surface 38 and an upper inclined surface 40 may be
optionally run and set in the first casing 22 above and adjacent the lower
whipstock 24. The lower inclined surface 38 of the upper whipstock 36
mates with the upper inclined surface 25 of the lower whipstock 24. The
upper inclined surface 40 of the upper whipstock 36 should be aligned with
the bottom of the casing window 32.
After the upper whipstock 36 has been set, the next step, as shown in FIG.
5, is to run a second casing 42 inside the first casing 22 and into the
lateral branch wellbore 34, with a stub portion 44 of the second casing 42
extending from the lateral branch wellbore 34 through the casing window 32
into the first casing 22. In an alternative embodiment of the present
invention, the step of installing the upper whipstock 36 may be omitted,
and the second casing 42 may be guided into the lateral branch wellbore 34
by the window remill pilot 26. After the second casing 42 is positioned in
the lateral branch wellbore 34, it is then set in place in a customary
manner by use of a setting substance 46, such as cement or other known
setting substances. As will be understood by those skilled in the art, the
cement 46 may be pumped down the interior of the second casing 42, back up
the annulus between the lateral branch wellbore 34 and the second casing
42, and up to, and preferably past, the casing window 32 in the first
casing 22. In other words, it is preferred that the cement 46 be pumped
out through the space between the casing window 32 and the second casing
42 onto the stub portion 44 of the second casing 42. After the cement 46
has dried, the next step, as shown in FIG. 6, is to mill the stub portion
44 of the second casing 42 flush with the inner diameter of the first
casing 22. The upper whipstock 36 is then retrieved and any debris
associated with milling the stub portion 44 is cleaned out in a customary
manner.
The steps described up to this point represent a common approach currently
in use to seal the junction between the first and second casings 22 and
42. This method, however, is believed not to be entirely satisfactory. One
major problem with relying on the cement 46 to seal the junction is that,
before it sets, it tends to flow downwardly, under the force of gravity,
away from the junction. In addition, even when the cement 46 stays in
place long enough to dry, due to its porous consistency upon drying, it
does not provide an optimum seal. In an effort to provide an improved
approach to sealing the junction between a central and a lateral branch
wellbore, the present invention was developed. The present invention, as
will be described more fully below, may be used in conjunction with the
above-described approach, either with or without the cementing step, and
with or without certain other steps, as will be more fully explained
below.
Referring now to FIG. 7, the next step of the method of the present
invention--after the stub portion 44 has been milled flush with the inner
diameter of the first casing 22, and after the second casing 42 has been
cemented in place, assuming the cementing step is used--is to use a
running tool (not shown) to install an in-situ polymerizable sealing
sleeve 48 into the first casing 22 adjacent the junction of the first and
second casings 22 and 42. The sealing sleeve 48 should be positioned so as
to extend across the casing window 32. After positioning the sleeve 48, it
should be polymerized and allowed to cure. In a specific embodiment, the
sealing sleeve 48 may be of the type described in U.S. Pat. No. 5,494,106,
which is incorporated herein by referenced, and in SPE 8202, a paper
entitled "In-Situ Polymerisation of an Inflatable Composite Sleeve to
Reline Damaged Tubing and Shut-Off Perforation" that was presented at the
1996 Offshore Technology Conference, held in Houston, Tex. Related sleeves
are disclosed in PCT applications WO 94-25655 and WO 96-01937. In a
specific embodiment, the sleeve 48 may include a cylindrical body 50
having a longitudinal bore 52 therethrough, and may be constructed of
fibers and polymerizable resins. The sleeve 48 may also include a
drillable sidewall 54 in the cylindrical body 50, and a resilient outer
skin 56 substantially covering the cylindrical body 50.
In a specific embodiment, the sleeve 48 may include a first orienting
device 58 operably connected at a first end of the sleeve 48, and, if
desired, a second orienting device 60 operably connected at an opposite or
second end of the sleeve 48. The function of the orienting devices 58 and
60 is to provide a means by which the lateral branch wellbore 34, and more
particularly, the second casing 42 disposed therein, may be located when
access is desired thereto, and a means for selectively directing a well
tool (not shown) into the second casing 42. The structure and operation of
the orienting devices 58 and 60 will be readily apparent to those of
ordinary skill in the art. For example, the orienting devices 58 and 60
may be of the type disclosed in U.S. Pat. No. 3,889,748 (see FIG. 1, and
the helical guide surface 63) and U.S. Pat. No. 4,106,563 (see FIG. 1A,
and the guide surface 34), both of which are commonly assigned hereto and
incorporated herein by reference. The scope of the present invention is
not to be limited to any particular orienting device.
After the sleeve 48 has been installed and allowed to cure, the next step
is to cut a window through the drillable sidewall 54 in the sleeve 48
adjacent the casing window 32 to provide access to the second casing 42.
Referring now to FIG. 8, this task is accomplished by using a running tool
(not shown) to run a window remill pilot 62--similar to, but diametrically
smaller than, the window mill pilot 26 shown in FIGS. 2 and 3--inside the
sleeve 48. The window remill pilot 62 is set in place such that it is
oriented and aligned with the second casing 42, which is now covered by
the sleeve 48. The window remill pilot 62 may be oriented off the lower
whipstock 24 or by one of the orienting devices 58 or 60, which, as
discussed above, may be connected to opposed ends of the sleeve 48.
After the window remill pilot 62 has been set in place, and after removing
the running tool (not shown) used to run the window mill pilot 62 into the
sleeve 48, the next step, as illustrated in FIG. 9, is to run a milling
tool, such as a tapered mill (not shown), into the window remill pilot 62,
which will guide the milling tool so that it will mill a sleeve window 64
through the sleeve 48. In a specific embodiment, the sleeve window 64 may
be milled flush with the inner diameter of the second casing 42. Referring
now to FIG. 10, the next step is to retrieve the window remill pilot 62,
and then remove the lower whipstock 24, either by retrieving it upwardly
through the sleeve 48 or by simply drilling it out, in a manner known to
those of skill in the art. When the operation is complete, the sleeve 48
will be installed in place and will be provided with the sleeve window 64,
as shown in FIG. 10, through which access may be had to the second casing
42. Thus, in accordance with an important object of the present invention,
the junction between the first and second casings 22 and 42 will be sealed
by the sealing sleeve 48, either as a primary seal, if the cementing step
is omitted, or as a back-up seal to the cement 46, if the cementing step
is carried out, as explained above. It is believed that the sealing method
and apparatus of the present invention overcomes the above-discussed
deficiencies associated with prior approaches to sealing the junction of a
central and lateral wellbore. Further, in accordance with another
important object of the present invention, if the sealing sleeve 48 of the
present invention is provided with at least one orienting device 58 or 60,
the second casing 42 may be located when access is desired thereto, and a
means for selectively directing a well tool (not shown) into the second
casing 42 disposed in the lateral branch wellbore 34 is available.
Moreover, the above objects are achieved by the present invention without
introducing significant restrictions in the central or lateral wellbores.
It is to be understood that the invention is not limited to the exact
details of construction, operation, exact materials or embodiments shown
and described, as obvious modifications and equivalents will be apparent
to one skilled in the art. For example, the step of running and setting
the window mill pilot 26 may be eliminated, and the lower whipstock 24 may
be used to divert the milling tool (not shown) and the drilling tool (also
not shown) to their desired locations. It should also be understood by
those of skill in the art that the use of the method and apparatus of the
present invention to reenter a central wellbore having one or more lateral
branch wellbores that have been sealed with cement, or other known sealing
substance, to provide a backup seal to the cement, or other sealing
substance, is intended to be within the spirit and scope of the present
invention. Accordingly, the invention is therefore to be limited only by
the scope of the appended claims.
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